The long-range goal of this research is to identify neural mechanisms for odor recognition and odor learning. The central olfactory network of the terrestrial mollusc Limax maximus will be used, which is particularly advantageous for a cellular and computational analysis of odor recognition and odor learning. This olfactory network, the procerebrum (PC), shows oscillatory dynamics and wave-like propagation of excitation, both of which are modified by odor-elicited receptor input. Specific aims of the proposed work will test the following hypotheses: (1) Odors produce unique spatial and temporal patterns of central activity. (2) Odor learning alters the central pattern elicited by an odor. (3) Learning-specific labeling of PC neurons identifies sites of odor memory. (4) Patterns of odor-elicited activity in PC output cells reflect odor learning. Methods: Electrophysiological and optical studies of PC activity in isolated nose-brain preparations will measure odor-elicited alterations in spatial and temporal patterns of activity in PC lobes from control and odor conditioned slugs. Electrodes implanted on the PC lobe in situ will be used both to record odor-elicited alterations in PC lobe activity and to perturb PC dynamics during odor-guided behavior. Intracellular recordings from Dil stained PC output cells responding to odor stimulation will assess the synaptic result of odor processing in the PC before and after odor conditioning. Health Relatedness: Understanding basic cellular and synaptic mechanisms of learning contributes directly to designing treatments for learning disorders such as mental retardation and Alzheimers disease.